Surveying instrument, level, and the like



J. W FRENCH SURVEYING INSTRUMENT, LEVEL, AND THE LIKE Mar. 13, 1923.

Filed Oct. 29, 1920 2 sheets-sheet 1 aaj.

Patented Mar, 13, 1923.

JAMES WEIR FRENCH, F ANNIESLAIID, GLASGOVI, SCOTLAND; ASSIGN'OR T0 BARR AND STROUD, LIMITED, ANNIESLAND, GLASGOSIV, SCOTLAN'D.

SURVEYING INSTRUMENT, LEVEL, AND THE LIKE.

Application filed October 29, 1920. Serial No. 420,535.

(GRANTED UNDER THE rnovrsrons or THE ACT or iiaaene, i921, 4i srar. Ii., .131 3.) f g To all whom it may concern.

Be it known that I, JAMES 1in: FRENCH, a subject of the King of Great Britain and Ireland, and of Caxton Street, Anniesland, Glasgow, Scotland, have'invented new and useful Improvements in or Connected with Surveying Instruments, Levels, and the like (for which application for patent in Great Britain has been made No. 15 L958, dated 10 July 28, 1919), of which the following is a specification. I v

This invention relates to the production of a new type of surveying, instrument comprising ,a telescope provided with two re flectors fixed to the telescope and located outside the incident end thereof, the two reflectors being arranged to direct into the telescope rays proceeding in alignment from opposite directions normal to the axis of the telescope, the telescope with its reflectors be ing mounted capable of rotation about the axis of-the telescope and mounted capable of angular adjustment about a trunnion axis transverse to the telescope and normal to the direction of the said rays, which trunnion axis turns with the telescope, the instrument being for use in determining levels or directions normal to an axis, hereinafter referred to as the axis of position, and in use be sub j ected to a preliminary process for setting in order to bring the axis of position normal to the direction in which the observations are to be subsequently made, the preliminary process involving successive observatlons 1n one and the same directions being made on an object by using the tworeflectors alter-- nately, in the process ofwhich the instrument is rotated about the axis of the tele scope, and by angular adjustment about the trunnion axis the instrument may thereby be set, in accordance with the mean ofthe ob servations made by using the two reflectors alternately, so that observations by both re,

flectors coincide each with the cross wire with which the eyepiece of the telescope may be provided. When this is done the axis of the telescope becomes the axis of position and is truly normal to the direction of the object, and surveying operations may then he proceeded with about that axis in the process of which one only of the reflectors is required to be made use of. The other reflector may bescreened. I

' Instruments according to this invention maybe so constructed that an erect image, of an object, a staff for example, under observation may be obtained without the use ofan erecting eyepiece and that the, tacheometric angle may be reckoned from a vertical axis.' Reflectors suitable for the purposes of this invention may comprise a prism combination so constructed that lightentering from one direction is reflected at right angles by an oblique surface of the prism combination into the telescope objective, and light proceeding in alignment from the opposite di: rection is reflected at right angles into" the telescope objective from another oblique surface of the prism combination normal to the first mentioned surface. may be transmitted through the first oblique surface, the second oblique surface being situated behind the first surface or they may be disposed side by side, and the relative position of the two reflecting surfaces must be such that the optical axis ofthe telescope 1 must pass through the line of intersection of the reflecting surfaces or through aline defined by the intersection of "two planes containing the respective reflecting surfaces.

Some examples of construction according to this invention will now be described with The second beam reference to the accompanying drawings, inv

Figure 1 is an elevation illustrating the optical bination. v

Figure 2 is a sectional elevation illustrating a modified arrangement of telescope and prism combination. j

Figure 3 is a sectional elevation of an eyepiece prism for use in association'with an instrument of the character illustrated at Figure 1.

Figure ll is a sectional elevation of anop tical system for use in association with instruments according to this invention, the form illustrated belng applicable for asso ciation in construction with an-instrument of the character illustrated at Figure 2.

Figures 5. and 7 are elevations. and Fig! ures 6,,and 8 are plans, respectively, illus parts of a telescope and prism comtrating two modified forms of prism com binations. i j V Figure'9 isian' elevation and F gure 10 is a sectional elevationof an instrument of the,

will be assumed tobe verticalv and constiincident 7 light.

tute. the, axis ofposition. One of the right angle faces of theprism A. is. arranged normal to the axis 1 'of the telescope. A part ofthe hypothenusal .face of the prism A is made light reflecting, for instance, by silvering, andthe remainingportion in the region at the centre of the face is not silvered to provide a window 2 through which lightfrom aprism B is adapted to pass. The prism B is placed with one of its right angle faces against the hypothenusal face of the prism A and arranged so as to cover the Window 2, thehypothenusal face of the prism B being normal to the The arrangement in this case is such that the prism A, has an incident face 3, and the prism B an incident face l which are presented in opposite directions, so that lightpassing into theprism A is reflected by the silvered part of its hypothenusal face into the telescope and light passing into the prism B is reflected by the right angle face 5 whichis made light reflecting through the window 2 into the telescope.

An instrument of this character is mounted capable of rotation about the axis of its telescope and of being set. say, with its axis approximately vertical, coincident more or less with the axis of position and then of being tested to ascertain whether the axis of rotation 1 is truly the axis of position by making two observations on an object, a staff for example, one byreflection from the prism A the other observation by reflection from the prism B, and ifthese observations are not coincident adjustment is required, suitable provision for which is made.

scope objective and the oblique reflectingfaces Qfth prism c mb n tio af I desired provisionma y be made whereby the observer looks in horizontally, for which purpose there maybe placed above the eyepiece aneyep ece prism 6 as shown at Figlr B c mprIsrng ,a gb lique reflect ng u face. 'In' this case the staifw'ill appear iiieas es verted and laterally reversed, necessitating the use of an erecting eyepiece or prism system if an erect image is desired. The eyepiece prism 6 may be mounted capable of rotation about theaxis of the telescope in order that its attitude relatively to the observer may be maintained when the telescope is rotated about the vertical axis.

In the arrangement illustrated at Figure 2, the position of the principal parts is inverted the prism combination A, B being at the top and the eyepiece atthe bottom. In this case 'an. eyepiece prism '7 comprising an oblique reflecting surface is provided in front of the eyepiece so arranged that the observer can look in'horizontally or obliquely. Theeyepiece prism 7 may be mounted capable of rotation so as to maintain its attitude relativelyto the observer when the telescope and line of sight are rotated.

Between the observers eye and the field of view of the telescope there maybeprovided as indicated at Figure 4: an optical system C of prisms and lenses so arranged as to erect the image when the observer is facing the objectjand enable thelevel of the line of sight of the observers eye tobe arranged at any desired position relatively to the line of sight of the prism combination A, B. v

In any of the arrangements shutters 8, 8, see Figure 2, for intercepting the rays proceeding in alignment from opposite c irections normal to the axis o'fthe telescope to obscure either of the lines ofsight may be provided.

In a surveying telescope of a'lrnown type in which the focussing is'efiecte'd by a displacement of the eyepiece the tacheometric angle is measured from the front focusof the objective, that is froma point on the object side of the objective equaltothe focal length. When the focussing is done by means of the displacement ofIa-n internal lens the position from which the tacheo metric angle is measured can be varied. In this invention the focussing lens may be so arranged that the tacheometric angle is reckonedvfrom the vertical axis of rot'atiog f of the telescope.

Figures 5 and 6 illustrate a modified form of prism combination in which theprism B is formed of a widtlrequal to thewidth of the window 2 which extends as a band across the face of the prism A. 4

Figures? and .8 i lustrate a modiiied forni of prism combination comprising prisms A and B arranged sicle by side, in which case no window is provided.

Theinstru'ment illustrated at Figi r'es V and 10, which is ofthecharacter described with reference to Figure 1, compi s a base part D which is supported onfleve'llihg feet E carried by a sta-ndF. Upon the base prisms A, B, of which A 6 about the part D a frame G is mounted capable of rotation about the vertical axis thereof, which may be rotated freely by hand when a screw H is released, or when the screw H is tightened rotated by means of gearing operated by a head H Upon the frame G, the instrument com-. prising the telescope designated K and only is seen, is mounted to swing about a a, horizontal trunnion support the axis L -of which is normal to the raysproceeding in alignment which are reflected into the telescope by the prisms A, B, angular, adjustment axis L being produced by operation of gear actuated by the" head L Mounted on the frameG is a spirit level N provided for ascertaining when the frame G is approximately level, and attached to the telescope K is an adjustable spirit level P arranged longitudinally normal .to the trunnion axis L, capable of adjustment relatively to the line of sight either'by an inclination of the spirit level P or by an alteration of the position of an index, with which the spirit level P is provided, relatively to the bubble, in which case either the index or the bubble may be displaced longitudinally. Thus the prism combination A, B and with it the telescope K and the spirit level P is rotatable about a more or less verticalaxis' in; order to direct either the forward or the backward line of sight upon-the staff being observed upon.

The method of adjusting a. surveying level made in accordancewith this invention may, for example, be as follows:

The verticality of the telescopeis roughly adjusted in both planes. with reference to the rough level N by means of the adjustable feet." The observer directs the line of sight in azimuth upon the staff and notes the reading on the cross wire of the eyepiece and also the reading of the spirit level P. He

then rotates the telescope about the vertical axis through 180 and views the staff along the second line of sight. He then swings the telescope about the horizontal axis L until the index of the spirit level P occupies the same position as before relatively to the bubble and again notes the reading of the staff at the cross wires of the telescope eyepiece. By a suitable swinging movement of the telescope about the axis L he then sets the cross wire upon the mean indication of two previous staff readings, and by a' suitable longitudinal movement of say the index of the spirit level P he restores the original relative position of index and the bubble. The line of sight then lies in a plane that is truly level in accordance with the indications of the spirit level P.

I claim 1. An instrument consisting of a telescope, reflectors fixed t the telescope located outside its incident end, the reflectors having two reflecting surfaces at right angles to one another arranged each at 45 to the optical axis of the telescope and presented towards the telescope for directing into the telescoperays proceeding in alignment from opposite directions normalto the axis of the telescope, the relative positions ofjthe two reflecting surfaces being such th-atthe optical axis of thetelescope passes through a line defined by-the intersection of two. planes containing the respective reflecting surfaces, a frame mounted capable of rotation about an upright, axis, and atrunnion support on the frame by which the telescope is carried, the'axis of which trunnion sup-1 port is transverse to the telescope and normal to the direction of the said rays and turns with the telescope and the frame, for the purposes set forth. Q I

2. An instrument consisting of a telescope, a prism combination fixed to the telescopelocated outside its incident end, the prism combination having. two reflecting surfaces at right angles to one another .arranged each :at 45 to the optical axis of the telescope and presented towardsthe telescope for'directing'into. the telescoperays 1 proceeding in alignment from opposite directions normal. to the axis of. the telescope, the relative positions of the "two reflecting surfaces beingsuch that the optical axis of. the telescope passes through a line definedby'the intersection of two planes containing the respective reflecting surfaces, a frame mounted capable of. rotation about an up right axis, and a trunnion "support on the frame by which the telescope is carried,

the axis of whichtrunnion support is trans-' verse to the telescope and normal to the di-frection of the said rays and turns with the telescope and the frame, for the purposes set forth. 3. An instrument consisting of a telescope, a prism combination fixed to the telescope located outside its incident end, the prism combination having a first and a second reflecting surface at right angles to one another arranged each at 45 to the optical axis of the telescope and presented towards the telescope, a window in the first reflecting surface, the second reflecting surface being situated behind the first, for directing into the telescope rays proceeding in alignment from opposite directions normal to the axis of the telescope, the relative positions of the two reflecting surfacesbeing such that the optical axis of the telescope passes through a line defined by the intersection of two planes containing the respective reflecting surfaces, a mounted capable of rotation about an-upright axis, and a trunnion support on the frame by which the telescope is carried, the

frame to .the optical' axis of the telescope and presentedtowards the t'eles'cope for directing in to the telescope rays proceeding in alignment from' opposite directions normal to the axis of the telescope, the relative positions of the two reflecting surfaces being such thatthe optical of'tlie telescope passes through a line defined by the 1ntersection 'of'two planesflcontaln ng the re- 1 spective' reflectingsurfaces, a frame mounted capable of rotation about anwrpright axis, a trunnion support in' the frame by which the telescope is carried, the axis of which trunnion support is transverse tothe telescope" and normal to the direction of the said rays and turns with the telescopeyand an adjustable spirit level attached to 'the telescope arranged longitudinally normal tozthe't-runnion axis, for thepurposesset forth.

5. An'instrument consisting of a telesco1tie,'refiectors;fixed tothe telescope located outside its incident end, the reflectors having two reflecting surfaces at right angles to one another arranged each at 415 to the optical aXis of the telescope and pre, sented towards the. telescope for directing into the telescoperays proceeding inwalignment from opposite directions normal to the 40 axis of the telescope, the relative positions of the two reflecting c surfaces being such that the optical axis of the telescope 1 passes through a linedefinedbv the intersection of two planes containing the respective reflecting surfaces, a frame mounted capable of rotationaboutuin upri'ght aXis,a-' trunnion support on the frame by Which the telescope is'c'arriech the axis of which trunnion support is-transve'rse to the telescope and normal to the direction of the said rays and turns withthe telescope, and meansfor screening one of the reflectors, for the purposes set forth. I

6. Aninstrumen't consisting of a telescope, reflectors fixed to the telescope located outside its inci'denten'd, the reflectors having two reflecting surfaces at right angles to' one another arranged "each at to the optical axis of the telescope andpresented towards'the telescope for directing into the telescope rays proceeding" in alignment "fro1n"opposite directions normal to the axisof the telescope, the relative positions of the twore'flecting surfaces being such that the optical axisof' the telescope passes througha line defined by the intertive reflecting surfacespa stand, levelling feet carried b'y thestandy-a base part supported on the levelling feet, a frame mounted on the "base part capable of rotation about a vertical axis on which frame the telescope is mounted-to swing about-a horizontal trunnion axis, means for rotating said frame, gear for adjusting the instru ment angularl'y aboutithe' trunnion axis,- a spirit level on the frame, anadju'stable spirit level attached to the telescope, and means for screening one "of the reflectors, for thepurposes set forth.

JAM-ES WEIR FRENCH.

'section of two. planes containing the'rejspec- 

